#define _CRT_SECURE_NO_WARNINGS 1
/********** Begin **********/

#include<stdio.h>
int main()
{
    double c = 0.0;
    int n, m = 0;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        m += i;
        c += (double)1 / m;
    }
    printf("s = %lf", c);
    return 0;
}




/********** End **********/